Cam guide drive mechanism for power-assisted chairs and the like

ABSTRACT

The chair of the present invention includes a power-assisted linear actuation drive mechanism having a modified nut or &#34;cam guide&#34; which is linearly moveable upon rotation of the power screw for selectively actuating the lift and tilt linkage mechanism for causing forward lifting and tilting movement of the chair when the motor is operated in a first direction. Rotation of the screw shaft in a second opposite direction acts to lower the chair to the normal seating position. Continued rotation in the second direction causes sequential operative extension of the leg rest assembly followed by angular reclining movement of the chair. This sequential operation of the leg rest assembly and the reclining linkage are independent and may be easily disabled to selectively eliminate either of the features.

This is a continuation of U.S. patent application Ser. No. 613,355,filed Nov. 14, 1990 now U.S. Pat. No. 5,061,010 which is acontinuation-in-part of U.S. patent application Ser. No. 425,384 filedOct. 18, 1989, now U.S. Pat. No. 4,993,777 which is a continuation ofU.S. patent application Ser. No. 196,750, filed May 20, 1988 nowabandoned.

BACKGROUND OF THE INVENTION

The present invention relates generally to power-assisted articles offurniture and, more particularly, to a multi-function chair having alinear actuation drive mechanism selectively operable for lifting andtilting the chair, extending and retracting a leg rest assembly andreclining the chair between upright and fully reclined positions.

Conventionally, power-assisted chairs typically include a motor-operatedlift mechanism for aiding invalids and those persons requiringassistance in entering or exiting the chair. More particularly,motor-operated lift mechanisms are interconnected between a stationarybase assembly and a moveable chair frame. Alternatively, somepower-assisted chairs include separate linkage mechanisms for permittingthe seat occupant to selectively extend and retract a leg rest assemblyand/or produce reclining angular movement between an "upright" positionand a "reclined" position.

Heretobefore, most conventional power-assisted chairs have not beenadapted to provide the lift and tilt function in combination with a legrest and/or reclining function. Those chairs which do provide such acombination of multi-positional functions generally require the use ofmultiple motors for driving (i.e., pushing) the separate linkages whichresults in extremely large and expensive chair units. In addition, mostpower-assisted chairs incorporate a drive mechanism which employs both apower "drive" function (i.e., for extending the leg rest, lifting thechair, and reclining the chair) and a power "return" function forreturning the chair to the normal seated position.

SUMMARY OF THE INVENTION

It is a purpose of this invention to provide a low profilepower-assisted drive mechanism that is reliable and efficient inoperation, durable, and relatively compact and simple in construction,and which is adapted to be used with upholstered recliner chairs as wellas other chairs.

It is also a purpose of the invention to provide a power-assisted drivemechanism confined with the base assembly of the chair which in thenormal seating position has the outer appearance of an ordinary chair.

Another purpose of the invention is to provide a lift base assembly forchairs that is driven by an electric motor and which includes means todisable the motor if the chair is in an improper condition or if anobstruction is encountered during movement of the assembly.

It is another purpose of the present invention to provide a singlepower-assisted linear actuation drive mechanism for selectivelyactuating a chair reclining linkage assembly and a leg rest linkageassembly, in addition to raising, lowering and tilting the chair on thelift base assembly.

It is still another object of the present invention to providespring-biased return means for substantially reducing the potential fordamage to the drive mechanism due to an obstruction encountered when theseat occupant attempts to return the chair to its normal seatingposition.

A base assembly according to a preferred form of the invention comprisesa stationary bottom frame and a movable upper frame to which a chair maybe secured. A motor operated lift and tilt linkage mechanism moves theupper frame and the chair. The motor-operated linkage mechanism nestsinside of the frames and the bottom of the chair, so that it is hiddenwhen the chair is in the normal seating position. Operation of the motorcause the lift and tilt linkage mechanism to raise or lower the upperframe under the control of a hand-operated switch which may be actuatedby a person using the chair.

More particularly, the motor-operated lift and tilt linkage mechanism ofthe present invention includes a front and lower H-shaped lift bar thatis pivoted to a central portion of the lower frame and to a frontportion of the upper frame. It also includes a rear and upper U-shapedtilt bar that is pivoted to a rear portion of the lower frame and afront portion of the upper frame. An electric motor, which drives thelift and tilt linkage mechanism, is pivotably secured to the rear of thelower frame and has a rotary power screw which extends through a nutthat is pivotally attached to an upstanding bracket on the cross bar ofthe H-shaped lift bar. With this arrangement, rotation of the screw inone direction pulls the nut rearwardly for raising the lift bar and tiltbar for elevating and tilting the upper frame. The weight of the chairand its occupant act in opposition to the rearward lifting movement ofthe nut. This opposition puts the screw shaft in tension and, ascompared with compressive loads associated with most conventional liftshaft designs, reduces the likelihood of shaft distortion for promotingimproved reliability, durability and more efficient performance of thelift assembly.

In a preferred form, the power-assisted linear actuation drive mechanismof the present invention includes a modified nut or "cam guide" which islinearly moveable upon rotation of the power screw for selectivelyactuating the lift and tilt linkage mechanism for causing forwardlifting and tilting movement of the chair when the motor is operated ina first direction. Rotation of the screw shaft in a second oppositedirection acts to lower the chair to the normal seating position.Continued rotation in the second direction causes sequential operativeextension of the leg rest assembly followed by angular recliningmovement of the chair. This sequential operation of the leg restassembly and the reclining linkage are independent and may be easilydisabled to selectively eliminate either of the features.

Other features and advantages of the present invention will becomeapparent upon consideration of the drawings and the description setforth hereinafter.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic side elevation of a reclinable upholsteredchair, with extendable footrest, in seated position mounted on a liftbase assembly embodying the invention;

FIG. 2 is a view similar to FIG. 1, but showing the lift base in fullyextended position, wherein it has lifted the rear of the chair and has,thereby, tilted the chair, parts of the operating mechanism beingomitted for clarity;

FIG. 3 is a somewhat schematic perspective view of the lift baseassembly of FIGS. 1 and 2 taken from the front with the chair removedand the base in the seated or down position;

FIG. 4 is a somewhat schematic perspective view of the lift baseassembly of FIG. 3 taken from the rear with the chair removed and thebase in the fully extended or lift position;

FIG. 5 is a vertical section through the base assembly of FIG. 3 but onan enlarged scale;

FIG. 6 is a vertical section through the base assembly of FIG. 4 but onan enlarged scale;

FIG. 7 is a wiring diagram for the assembly;

FIG. 7A is a view showing operation of the stop switch by the chair;

FIGS. 8A through 8D illustrate the various operative seating positionsassociated with selective actuation of a power-assisted cam actuationdrive mechanism incorporated into a second embodiment of amulti-functional chair according to the present invention;

FIG. 9 is a plan view of the left-side portion of the chair frame, withupholstery removed, illustrating the various components of thepower-assisted cam actuation drive mechanism which are provided forselectively operating the chair lift linkage mechanism, a reclininglinkage assembly and a leg rest linkage assembly;

FIG. 10 is a vertical cross-sectional view, similar to FIG. 5, throughthe multi-functional chair of FIG. 8;

FIG. 11 is a vertical cross-sectional view, similar to FIG. 6, throughthe multi-functional assembly of FIG. 8;

FIG. 12 is an opposite vertical cross-sectional view showing the legrest linkage assembly in a fully extended position;

FIG. 13 is a vertical cross-sectional view illustrating the operativeposition of the reclining linkage following extension of the leg restlinkage assembly; and

FIG. 14 is an exploded perspective view of the cam guide and followerassemblies of the cam actuation drive mechanism.

DETAILED DESCRIPTION OF THE EMBODIMENT OF THE INVENTION

A lift base assembly according to the present invention, is shown inFIG. 1 supporting an upholstered chair 3 in a normal seated position. InFIG. 2 it is shown lifting chair 3 to a tilted position that makes iteasier for a person to enter or leave the chair. Any of a wide varietyof chair constructions can be used with base assembly 1. The well-knowchair sold by the assignee hereof under the registered trademarkRECLINA-REST is an example of one that can be mounted on the base 1 andit is shown very schematically in the drawings. U.S. Pat. No. 4,367,895,issued Jan. 11, 1983, entitled Reclinable Chair, shows many structuraldetails of the RECLINA-REST chair. Chair 3 has a frame 5 with side arms7, a seat assembly 8 defined by a seat back 9 that may recline inresponse to pressure from the back of an occupant and a seat portion 11that moves simultaneously with seat back 9. Chair 3 also includes anextensible leg rest assembly 13. Leg rest assembly 13 may be manuallyoperated through a mechanism (not shown herein but shown in U.S. Pat.No. 4,367,895) by rotation of a square cross shaft 15 (FIG. 5) thatextends between the opposite sides of chair frame 5 via an externalhandle 17 located below arm rest 7 where it can be easily reached by aperson occupying the chair.

In the embodiment shown, the fore and aft length 19 of base 1 is about287/8 inches in the seated position of FIG. 1 and in the fully extendedposition of FIG. 2. With the particular chair 3 selected as an example,the height 21 of seat 11 above the floor is about 17 inches in theseated position of FIG. 1 and about 18 inches in the fully elevatedposition of FIG. 2. Normal height 21 for the chair 3 in the absence ofbase 1 would be about 15 inches. The overall height 23 of chair 3 in theseated position of FIG. 1 is about 41 inches and in the fully extendedposition of FIG. 2 it is about 551/2 inches. The angle of forward tilt25 in the fully extended position of FIG. 2 is preferably about 29degrees. It will be appreciated that these dimensions are merelyexemplary in nature and are not intended to limit the present invention.

Base assembly 1 has a stationary, rectangular, bottom frame member 31that rests on the floor and a movable, rectangular, upper frame member33 on which chair 3 is removably but securely attached by suitablefasteners (not shown). Bottom frame member 31 includes wooden left andright hand side members 35 and 37, respectively, and these are rigidwith a wooden front cross member 39. Side members 35 and 37 may havesuitable pads 41 (FIG. 5) on the bottom to actually engage the floor.

Upper frame member 33 has wooden left and right hand side members 45 and47, respectively, and these are rigid with a wooden rear cross member49. Soft rubber-like pads 50 (FIG. 6) on the bottoms of upper sidemembers 45 and 47 help transfer vertical chair loads into bottom sidemember 35 and 37 in the seated position of chair 3. The wooden outerportions of base assembly 1 give it the appearance of an ordinary chairbase. The lift mechanism to be described nests inside of the woodenframe members and the bottom of chair 3 and, as indicated above, baseassembly 1 is of low profile and increases the seat height by only about2 inches.

The front of upper frame member 33 is reinforced by a U-shaped metalpivot bracket 51. This has metal side plates 53 that are securelyaffixed to the inside faces of wooden side members 45 and 47 asindicated at 55. The front ends of side plates 53 are rigid withreinforcements and pivot plates 57 which extend below wooden sidemembers 45 and 47 into the confines of lower frame 31 as seen in FIG. 6.Metal pivot bracket 51 includes a rectangular tube 59 that is a frontcross piece extending between pivot plates 57 on opposite sides and maderigid with them, as by welding. A round metal tubular cross bracingpiece 61 located somewhat below and to the rear of cross piece 59 alsoextends between pivot plates 57 and is made rigid with them, as bywelding.

The rear of lower frame member 31 is reinforced by a transverse metalpivot bracket member 71 that includes metal side plates 73 that aresecurely affixed to the inside faces of wooden side members 35 and 37 asindicated at 75. Pivot bracket 71 also includes a rectangular tube 79that is a rear cross piece extending between plates 73 on opposite sidesand made rigid with them, as by welding and gussets 81 (FIG. 4). Anothertransverse rectangular tube 83 is seated on top of tube 79 and is maderigid with it, as by welding. Tubes 79 and 83 form a T-shaped loadcarrying component of lift base assembly 1. The height of tube 79 issuch that tube 83 is located within the confines of upper frame 33.

Top tube 83 terminates at each end a slight distance inwardly from sideplates 73. At each end, i.e., adjacent side legs 45 and 47, it has aU-shaped bracket 85 rigidly affixed to it, as by welding. These receivethe rear ends of side legs 87 of a U-shaped upper tilt bar member 89.Side legs 87 are formed of square metal tubing and at their front endsthey are rigidly affixed, as by welding, to opposite ends of a frontcross piece 91, also a square metal tube. The rear ends of upper tiltbar side legs 87 that fit inside U-shaped brackets 85 on lower framemember 31 are pivotally attached to the opposite sides of the bracketsas indicated at 93. As seen best in FIG. 5, the height of combined tubes79 and 83 is such that side legs 87 are substantially horizontal whenlift assembly 1 is in the fully lowered or seated position. The upper orfront ends of side legs 87 are pivotally attached to pivot plates 57 onthe front of upper frame member 33 as indicated at 95.

Tilt bar member 89 is a part of lift and tilt linkage mechanism 97provided for operating base lift assembly 1. This mechanism alsoincludes a lower lift bar member 99 that is pivoted at its rear end to acentral portion of lower frame member 31 and at its upper end to pivotplates 57 of the upper frame member 33. Lower lift bar member 99 issubstantially H-shaped and has left and right hand side legs 101 thatare spaced apart the same amount as side legs 87 of the upper tilt bar89 and are also formed of square metal tubing of the same cross sectionwhereby legs 101 are coplanar with legs 87, though substantially shorterin length. A rectangular metal tube 103, similar to tube 79, extendstransversely between side legs 101 and its opposite ends are made rigidwith them, as by welding, at central portions of legs 101 as seen bestin FIG. 6. The lower and rear ends of side legs 101 are pivotallyattached at pivot 105 to brackets 107 that are rigidly affixed to theinside faces of side legs 35 and 37, as indicated at 109. The upper andfront ends of legs 101 are pivotally attached to lower portions of thesquare pivot plates 57 as indicated at pivot 111. Reinforcement bars 113maintain parallelism of upper and lower pivots 95 and 111 and areconnected at their upper and rear ends to pivot plates 57 by way ofpivots 95 and at their lower and front ends to pivot plates 57 by way ofpivots 111. The bars 113 are cutout at 115 so that they can pass closeto the rear of round cross brace tube 61.

As seen best in FIG. 5 the various parts of tilt bar 89 and lift bar 99,forming lift and tilt linkage mechanism 97, are confined within therectangular upper and lower frames 33 and 31, respectively, when baseassembly 1 is in the lowered or normal seating position. Thus, the liftand tilt mechanism is low profile and compact.

Power-assist means, such as an electric motor 121, is connected to lowerlift bar 99 for arcuately pivoting it up or down about pivots 105 and,thereby for operatively driving lift linkage mechanism 97. Motor 121 hasa rigid rearwardly extending flange 123 which fits between and ispivotally attached at pivot 125 to the two sides of a U-shaped pivotbracket 127 that is welded to a central portion of top cross piece 83 ofpivot bracket member 71 of lower base member 31. Motor 121 isselectively operable for rotating a screw shaft 129 in either a first orsecond direction. Both motor 121 and its rotary screw shaft 129 canarcuately swing up and down in a generally vertical plane about pivot125. Screw shaft 129 extends through and drives an internally threadedsleeve or nut 131 so that sleeve 131 moves forwardly or rearwardly alongthe length of shaft 129 upon rotation of shaft 129 in one of the firstand second directions. The front end of sleeve 131 is located betweenside surfaces 133 of tall U-shaped pivot bracket 135 and is pivotallyattached to them as indicated at pivots 137, the axis of pivot 137 beingparallel to but between the axes of pivots 105 and 111. U-shaped bracket135 is centrally located on top of cross piece 103 of lower lift bar 99and is made rigid with it, as by welding. As seen best in FIG. 5,bracket 135 projects only a little above the confines of upper frame 33,within available space inside chair 3, thereby maintaining thecompactness and low profile of lift base assembly 1.

Comparing FIGS. 5 and 6, or FIGS. 3 and 4, it will be seen that in theseating or lowered position of chair 3, sleeve 131 is positioned nearthe front or outer end of threaded rotary screw shaft 129. Lifting ofchair 3 is accomplished by energizing motor 121 to rotate screw shaft129 in a direction that draws sleeve 131 toward the motor. This pullspivot 137 rearwardly for causing lift bar member 99 to pivot upwardlyabout pivots 105. This upward pivotal movement is transmitted throughpivots 111 at the front ends of lift bar member 99 for lifting of upperframe member 33. The path of the "lifting" movement is determined bylower lift bar side legs 101 and, also, by the longer upper tilt barside legs 87. Front pivots 95 on upper frame 33 lift the front ends ofside legs 87 which, therefore, pivot upwardly about their rear pivotconnections 93 to lower frame member 31. Upper tilt arm 89 has a largervertical component of travel during lifting than does lower lift barmember 99. Therefore, the rear end of chair 3 is "tilted" upwardly aboutpivots 111 in amounts proportional to the amount of lift. As previouslyindicated (FIG. 2), a chair entry and exit angle 25 of about 29 degreesis preferable. This is determined by contact of the rear end of sleeve131 with a limit switch trigger 141 provided on or near motor 121 whichopens the electrical circuit and stops motor 121. To lower chair 3,rotation of screw shaft 129 is simply reversed.

Motor 121 is preferably of a type that has means to sense a change inthe state of force on linkage system 97 and to disable motor 121 inresponse to such a change. A motor of this type is sold by MaxwellProducts, Inc. of Cerritos, Calif. and is described in U.S. Pat. No.4,407,030, issued Oct. 4, 1983, entitled "Safety Device for anAdjustable Bed". It will be seen that in the present construction, theweight of chair 3 and an occupant of the chair will place a downwardforce on pivots 111 which tend to apply a forward force on pivots 137,thus putting screw shaft 129 in tension. If a foreign object orresistance is encountered by upper frame member 33 a it is beinglowered, there will be a change in the tension load on screw shaft 129since the effect of the obstruction will be to apply an opposite load(i.e. compression) to the screw. Preferably, motor 121 has meansincorporated in its assembly to sense this change of state and disablethe motor until the obstruction is removed. When upper frame 33 islowered to the degree that it contacts lower frame 31 by way of pads 50,motor 121 will sense the change in resistance and be shut off.

Referring to FIG. 7, the electrical control system 201 for motor 121 isshown to preferably include a three-prong grounding attachment plug 203which fits into a grounding-type electrical receptacle (not shown) inthe general proximity to where base assembly 1 is used for providingelectrical current to operate the lift assembly. Plug 203 has aninsulated cable or power cord 205 of suitable length containing agrounding conductor 207 and two current carrying conductors 209 and 211.

Motor 121 has an insulated power cord 213 which contains a groundingconductor 215 and three current carrying conductors 217, 219 and 221.The three current carrying conductors 217, 219 and 221 are connected toterminals 223, 225 and 227, respectively, of a male socket 229. Malesocket 229 mates with female socket 231 so that male socket terminals223, 225 and 227 are electrically connected to female socket terminals233, 235 and 237, respectively. Current carrying conductor 211 of powercord 205 is connected to female socket terminal 235. The other terminals233 and 237 of female socket terminal 235 are connected by conductors239 and 241, respectively, to terminals 243 and 245, respectively, of asecond female socket 247. A third terminal 249 of female socket 247 isconnected to current carrying conductor 209 of power cord 205.

Socket 247 mates with male socket 251 so that male socket terminals 253,255 and 257 are electrically connected to terminals 243, 245 and 249,respectively, of female socket 247. Terminal 253 of male socket 251 isconnected by conductor 259 to terminal 261 of a third female socket 263.A second terminal 265 of socket 263 is connected to conductor 267contained in hand control cord 269. Hand control cord 269, also,contains conductor 271 which is electrically connected to terminal 255of male socket 251 and conductor 273 which is electrically connected toterminal 257 of male socket 251.

Hand control cord 269 terminates in a hand operated switch 275 housedwithin switch housing 277 that may be mounted to a side arm 7 of chairframe 5 or, alternatively, held and operated by a person using the chair3. Preferably, when switch 275 is operated to connect conductors 271 and273 electrical power is supplied to motor 121 to rotate screw shaft 129in a direction to cause chair 3 to lower. When switch 275 is operated toconnect conductors 271 and 267 power is supplied to rotate screw shaft129 in the opposite direction for elevating chair 3 provided that theshut-off switch 279 is made or closed.

Shut-off switch 279 has a cord 281 containing current carryingconductors 283 and 285. Conductors 283 and 285 are electricallyconnected to terminals 287 and 289, respectively, of a male socket 291.Socket 291 mates with female socket 263 to electrically connect itsterminals 287 and 289 to terminals 261 and 265, respectively, of thefemale socket.

The sockets 229, 231, 243, 251, 263 and 291 are preferably housed withina junction box 293 that may be rigidly secured (not shown) to crosspiece 79 at the rear of lower frame member 31. The grounding wires 207and 215 have terminals 295 and 297, respectively that may be connected(not shown) to the metal box.

Referring to FIG. 7A, the reference numbers in parentheses (i.e., 69,281 and 283) are reference numbers used in the aforementioned U.S. Pat.No. 4,367,895 (see FIG. 6 of the patent) to designate certain structuralfeatures of the chair shown in that patent. As already indicated, chair3, herein, may embody construction features shown in the patent (thoughthe tracks 29 and related parts providing fore and aft movementresponsive to back recline will be omitted in chair 3). A feature ofchair 3 and the chair in the patent is that chair frame 5 tilts to raisethe front edge whenever leg rest assembly 13 is moved away from itsstowed position, shown herein, and/or whenever seat back 9 is reclinedfrom its upright position shown herein. Thus, angular tilt of chairframe 5 signifies that leg rest assembly 13 is at least partiallyelevated and/or seat back 9 is at least partially reclined. Referencenumber (69) in the patent designates a front vertical post in chairframe 5 located approximately midway between the left and right sides ofthe chair. It will move up due to tilt of chair frame 5. Thus, as showin FIG. 7A, an angle shaped bracket 301 may be secured by screw 303 topost (69) in such a position that it engages and makes stop switch 279when chair 3 is in its fully upright position with leg rest assembly 13in its fully retracted position. As seen from the circuit diagram ofFIG. 7, if stop switch 279 and switch 275 are pressed to interconnectconductors 267 and 271, current is able to flow through the variousconductors to rotate lift motor 121. On the other hand, if switch 279 isopen due to bracket 301 being raised by tilt of chair frame 5, currentcannot reach motor 121. It is preferred that this control by switch 279be applied to the lift mode so that chair 3 and upper frame 33 will notelevate if seat back 9 is reclined or leg rest assembly 13 is elevated.On the other hand, if switch 275 is pressed to interconnect conductors273 and 271, current is able to flow through various conductors toenergize lift motor 121 for rotating screw shaft 129 in a direction tolower chair 3.

In the lowered position of lift base assembly 1, the wooden outer partsof lower and upper frames 31 and 33, respectively, give the appearanceof an ordinary base for chair 3. The compact, low profile of electricmotor 121 and lift linkage mechanism 97 enable it to fit for the mostpart within the confines of the upper and lower frames, inside thebottom of chair 3, and below cross shaft 15.

When circuit 201 is activated by way of switch 275 to elevate upperframe 33, lift motor 121 is energized to rotate screw shaft 129 in adirection to pull nut 131 toward the rear of lift base assembly 1 andmotor 121. Such movement of nut 131 pulls its pivot 137 rearwardly so asto pull the top of bracket 135. Since bracket 135 is secured to thesturdy H-shaped lift bar member 99 such movement of nut 131 causes liftbar member 99 to pivot upwardly about pivots 105 on lower frame 31. Thisis accompanied by upward pivoting of motor 121 for moving screw shaft129 upwardly through an arcuate path. The upward movement of lift barmember 99 raises pivots 111 which, thereby, raises the front end ofupper frame 33. However, the sturdy U-shaped tilt bar member 89 is alsopivoted at pivot 91 to side plates 57 and as these pivots are elevated,tilt bar member 89 pivots upwardly about its pivots 93 with respect torear cross piece 71 of lower frame 31. Since tilt bar member 89 islonger than lift bar member 99, it forces upper frame 33 to tilt aboutthe axis of lift member pivots 111, thereby raising the rear of upperframe 33 so that upper frame 33 goes from a substantially horizontallowered position to an inclined elevated position. When nut 131 reacheslimit switch 141, motor 121 is stopped for holding chair 3 in the liftedpositions of FIGS. 2 and 6 in which it is easier for a person to beseated or to leave chair 3.

When it is desired to lower chair 3, circuit 201 is activated by way ofswitch 275 to lower upper frame 33. Lift motor 121 is energized torotate screw shaft 129 in an opposite direction to move nut 131forwardly away from motor 121. This will produce pivotable action oflift linkage mechanism 97 which is the reverse of that previouslydescribed. When upper frame 33 engages lower frame 31, or if anobstruction is encountered before complete lowering, motor 121 willsense the change in load on screw shaft 129 and shut off (i.e.,de-energized) as previously described.

During both elevation and lowering, upper frame 33 can be stopped andretained in any desired position by discontinuing actuation of switch275. As can be seen, the sturdy, rugged construction of lift linkagemechanism 97 enables it to solidly support the weight of a chair andoccupant with stability and durability.

Turning now to a multi-function chair 300 embodied in FIGS. 8 through14, many of the components and sub-assembles are identical orsubstantially similar to that previously described with reference to theembodiment illustrated in FIGS. 1 through 7. More particularly,multi-function chair 300 embodies a power-assisted cam actuation drivemechanism 301 adapted for selective actuation of a reclining linkageassembly 303 and leg rest assembly 13 in addition to operation of liftlinkage assembly 97'. In general, the power-assisted cam actuation drivemechanism 301 provides for sequentially actuating leg rest assembly 13and the reclining linkage 303 utilizing a single motor 121' and amodified sleeve or nut, hereafter referred to as cam guide 302. Morespecifically, cam guide 302 is adapted to move linearly relative toscrew shaft 129 for sequentially driving a leg rest follower assembly304 and a recliner follower assembly 306 which, in turn, are operativelycoupled to leg rest assembly 13 and reclining linkage 303, respectively.Thus, in the embodiment illustrated in FIGS. 8 through 14, identicalreference numbers are used to identify substantially similar structure.As will be appreciated, the use of a single linear actuation drivesystem such as cam actuation drive mechanism 301 provides forselectively lifting and tilting chair 300 (via lift and tilt linkage97'), extending and retracting leg rest assembly 13 (via leg restfollower assembly 304), and angularly moving seat back 9 and seat 11 ofseat assembly 8 between an "upright" and a "reclined" position (viarecliner follower assembly 306).

With particular reference to FIGS. 8A through 8D, various operativepositions of multi-function chair 300 are illustrated. FIG. 8A showsupholstered chair 300 in a "normal" seated or "upright" position. FIG.8B illustrates chair 300 "lifted" to a forward-tilted position uponactuation of lift and tilt mechanism 97' for making it easier for aperson to enter or exit chair 300. FIG. 8C illustrates leg rest assembly13 fully extended with chair 300 in an upright seating position.Finally, FIG. 8D illustrates chair 300 having seat assembly 8 angularlymoved to a fully "reclined" position following extension of leg restassembly 13.

As previously mentioned, chair 300 is preferably made up of severalcomponents and assemblies herebefore described and which include liftbase assembly 1, chair frame 5, seat back 9, seat portion 11, leg restassembly 13 and a modified lift and tilt mechanism 97'. Chair frame 5has left and right side members 308 having rearwardly sloping uprights312 with side members 308 being interconnected by a rear cross member314 and front top and bottom transverse cross rails 316 and 318,respectively, which are joined together by side bracket plates 320. Sidebracket plates 320 are secured to vertical uprights 322 located at thefront end of chair frame 5. Chair frame 5 is mounted outside andgenerally on top of base lift assembly 1 and is pivotally securedthereto about a pivot 319 between a bracket 324 provided on an innerwall of side members 308 and a second bracket 323 secured to an uppersurface of side members 45 and 47 of upper frame 33. A leg rest board orpanel 330 is supported upon chair frame 5 by a pair of pantograph legrest linkage assemblies 332 an example of which is clearly illustratedand described in the U.S. Pat. No. 3,588,170 to E. M. Knabusch et al.,issued Jun. 28, 1971 for "Motor-Operated Reclining Chair", thespecification and drawings of which are expressly incorporated byreference herein. It is to be understood that pantograph linkages 332are applied to both sides of chair frame 5 but since both are exactlyalike, only one will be described herein in detail.

As best seen in FIG. 9, square drive shaft 15 extends transversely tochair frame 5 and is supported from inner walls of chair frame sidemembers 308 for rotational movement. An L-shaped bracket 335 is coupledfor rotation with drive shaft 15 and includes down-turned operating arms336. An actuating or long drive link 338 of pantograph linkage 332 ispivotally secured about a pivot 340 to a lower end of arm 336, with theopposite end of link 338 being pivotally secured about a pivot 342 to alink 344. Link 344 is pivotally secured about a pivot 346 to a link 348which is pivotally secured about a pivot 350 to a mounting bracket 352,one of which is mounted near each lateral end of leg rest panel 330. Apivot 354 secures one end of link 356 to the opposite end of mountingbracket 352 while its opposite end is pivotally secured about a pivot358 to a link 360 which is pivotally secured to a bracket 362 supportedon top rail 316 of chair assembly 5 about a pivot 364. Link 356 issecured to link 344 by a pivot 366 and link 338 is joined to link 360 bya pivot 368. A brace or "spacing" link 370 having a centralstrengthening rib 372 is pivotally secured to at one end to bracket 362about pivot 364 and is journally connected at its opposite end to squaredrive shaft 15. Brace links 370 prevent any substantial bending of thesquare drive shaft 15 through the operation of cam guide 302 whenactuating leg rest assembly 13.

With continued reference to FIGS. 10 through 13, a reclining linkageassembly 303 is provided for causing reclining angular movement betweenseat frame 11 and seat back 9. Reclining linkage includes a front swinglinkage assembly 365 and rear swing linkage 400. More particularly,front swing linkage 365 includes a pivot 328 associated with side platebracket 320 which supports an S-shaped link 380, the lower end of whichis pivotally secured about a pivot 382 to a first end of link 384. Theopposite end of link 384 is pivotally connected at pivot 385 to a lowerend of link 386 which, in turn, is pivotally secured about a pivot 388associated with bracket 390 attached to a forward upper surface of siderails 45 of upper frame member 33. The upper end of link 386 ispivotally connected to one end of J-shaped toggle link 394 with theopposite end of J-shaped toggle link 394 being pivotably connected toL-shaped bracket 335 which is secured for rotation on square drive rod15. The upper end of S-shaped links 380 are pivoted on pins 396 on leftand right side rails 395 of seat frame 11. As will be describedhereinafter in greater detail, the interaction between the variouslinkages associated with front swing linkage 365 cause rearward tiltingof chair frame 5 about pivot 319 relative to base assembly 1 uponextension of leg rest assembly 13. More particularly, upon drive shaft15 being driven to rotate in a counterclockwise direction (FIG. 10),link 386 pivots about pivot 388 on bracket 390 to cause link 384 todrive the front of chair frame 5 upwardly and rearwardly.

Also forming part of reclining linkage assembly 303 is a rear swinglinkage 400 including a bracket 402 secured to each of seat frame siderails 395 near the rear end thereof. Bracket 402 has an upwardlyextending rear portion 404 and a downwardly extending forward portion406. An S-shaped link 408 is pivotally secured about a pivot 410 toupstanding rear portion 404 and a link 412 is pivotally secured about apivot 414 to downwardly extending forward portion 406, the structurebeing somewhat similar to that illustrated and described in theabove-mentioned U.S. Pat. No. 3,588,170.

An arm link 416 is secured to uprights 312 of chair frame 5 by screws,rivets or other reliable securing means. The upper ends of S-shapedlinks 408 are pivotably secured to arm links 416. Back frame 9 ismounted to the upper end of S-shaped links 408 for pivotal movementrelative to uprights 312. With this arrangement, back frame 9 issupported for forward and rearward reclining movement. The lower end ofS-shaped link 408 is pivotally secured about a pivot 420 to an offsetlink 422, the opposite end of which is coupled to a square tubularcrossbar 424 and to which the opposite end of link 412 is pivotallysecured. It is to be understood that similar linkages 412 and 422 on theopposite side of seat frame 9 are likewise secured to the opposite endof the crossbar 424. A spring member 42 is attached between an undersidesurface of side frames 395 of seat frame 11 and cross rail 314 of chairframe 5 for normally biasing rear swing linkage 400 toward its uprightposition (FIG. 10).

In accordance with the novel features encompassed in multi-functionchair 300 shown in FIGS. 8 through 14, lift and tilt linkage mechanism97' has been modified to include tall L-shaped pivot brackets 426, whichare located on opposite sides of screw shaft 129 and rigidly secured toa top surface of cross piece 103 of lower lift bar 99, such as by boltsand/or welding. L-shaped pivot brackets 426 are spaced to permit camguide 302 to move linearly (fore and aft) therebetween and includeelongated slots 428. A torque tube 430 is provided which extendstransversely between side legs 87 of U-shaped tilt bar member 89. Torquetube 430 is located in close proximity to front cross piece 91 fordefining pivot point 95 and about which brackets 113 are pivotallysecured. Guide pins 432 are fixed to opposite transversely extendingboss portions 434 of cam guide 302 so as to project through slots 428.As noted, screw shaft 129 extends through and drives internally threadedcam guide 302 such that cam guide 302 moves forwardly or rearwardlyalong the length of screw shaft 129 upon selective energization of motor121'.

As will be appreciated, and in particular reference to FIG. 10, whenchair 300 in the "normal" seating (i.e., lowered and upright) position,cam guide 302 is positioned near a central portion of screw shaft 129.Lifting and tilting of chair 300 is accomplished by selectivelyenergizing motor 121' to rotate shaft 129 in a direction that draws camguide 302 rearwardly toward motor 121'. Following a slight amount ofinitial rotation of shaft 129, cam guide 302 moves rearwardly until pins432 engage the rearward end stop surface of slots 428 such thatcontinued rotation of screw shaft 129 causes lift bar member 99 to pivotupwardly about pivot 105 for moving chair frame 5 to the position shownin FIG. 11. Except for the modification described, the operation of liftlinkage assembly 97' is substantially identical to that previouslydescribed herein.

Another feature of chair 300 of the present invention encompasseselimination of a "power pinch" condition upon a foreign object orresistances encountered by upper frame 33 as it is being lowered. Asmentioned, motor 121 of the first embodiment incorporated internal meansadapted to sense the change in loading on screw shaft 129 for disablingthe motor. As such motor 121 was also adapted to shut off when upperframe 33 contacted lower frame 31. However, cam drive mechanism 301 isadapted to permit continued forward movement of cam guide 302 relativeto screw shaft 129 when upper frame 33 is lowered into contact withlower frame 31 (FIG. 10) for selectively actuating leg rest assembly 13and reclining linkage assembly 303. More particularly, the mechanicalinteraction of cam guide 302 with lift linkage assembly 97' is such thatpins 432 are free to move forwardly in slots 428 when an obstruction isencountered upon lowering chair frame 5 for eliminating the "powerpinch" condition.

With particular reference now to FIGS. 9 and 12 through 14, means areprovided for selectively actuating leg rest assembly 13 and reclininglinkage assembly 303 upon selective continued energization of motor121'. More particularly, first follower assembly 304 is concentricallymounted for pivotable movement on a portion of torque tube 430. Firstfollower assembly 304 is provided for operatively rotating drive rod 15for causing power-assisted actuation of leg rest pantograph linkages332. First follower assembly 304 includes a first tubular sleeve 442concentrically supported on torque tube 430 to which is secured a firstcam lever 444 and a first cam link 446. First cam lever 444 and firstcam link 446 are rigidly secured to first tubular sleeve 442 such as bywelding and a spacer bar 448 is provided therebetween for supplyingadditional rigidity. Attached to an upper end of first cam lever 446 isa follower member, such as nylon roller 450, adapted to rollingly engagea first cam surface 452 formed on an undersided surface of cam guide 302and is generally adjacent to a front transverse end 453 thereof.

First cam link 446 is pivotally connected at its upper end to a firstend of toggle link 454, the opposite end of which is connected to adrive link 456. Drive link 456 is coupled to drive shaft 15 for rotationtherewith. As such, first follower assembly 304 is designed to interactwith first cam surface 452 of cam guide 302 for selectively actuatingleg rest linkages 332 by causing rotation of drive shaft 15. Moreparticularly, as cam guide 302 moves forwardly on screw shaft 129, firstroller 450 engages first cam surface such that first cam link 446 isforwardly pivoted o torque tube 430 for causing corresponding angularmovement of drive shaft 15 which, in turn, causes pantograph linkages332 to extend. Furthermore, a pair of left and right springs 480 areprovided for interconnecting each pantograph linkages 332 to a bracket482 rigidly supported from rear cross frame 49. Springs 480 are providedfor biasing first follower assembly 304 rearwardly for returning legrest assembly 13 to its retracted "stored" position once first camsurface 452 disengages follower 450 upon reversing the rotation of screwshaft 129.

Second follower assembly 306 is also installed concentrically abouttorque tube 430 and includes a second cam lever 462, a second tubularsleeve 464, a second cam link 466 and a second spacer bar 468. A secondroller 451 is supported from second cam lever 462 and is adapted torollingly engage a second cam surface 470 formed on the right halfunderside surface of cam guide 302. Second cam surface 470 is locatedsufficiently rearward of first cam surface 452 to permit full extensionof leg rest assembly 13 prior to initiation of any reclining movement.This orientation of first cam surface 452 relative to second cam surface470 is clearly illustrated in reference to FIG. 12. The upper end ofsecond cam link 466 is pivotally connected to an attach link 472provided for connecting second cam link 466 to tubular cross bar 424. Assuch, second cam surface 470 acts on second follower 451 of secondfollower assembly 306 for moving cross bar 424 forwardly upon forwardmovement of cam guide 302. Such movement of cross bar 424 causescorresponding movement of reclining linkage assembly 303 for movingchair 300 to the "reclined" position of FIG. 13.

One end of a spring link 474 is interconnected to second cam link 466and the other end of spring link 474 supports one end of a spring member476. The other end of spring member 476 is supported from a bracket 478rigidly secured to cross rail 49 of upper frame 33. Spring 476 isprovided for urging second cam link 466 and, in turn, second followerassembly 306 rearwardly so as to bias reclining linkage 303 and, inturn, the seat assembly toward the "upright" position. Therefore, secondfollower assembly 306 is also adapted to provide spring-biased returnmeans.

In operation, when the hand control is selectively operated by the seatoccupant to drive motor 121' in a first direction, chair 300 moves fromthe "normal" position shown in FIG. 8A to the forward "lifted" positionshown in FIG. 8B. More particularly, rotation in this first directioncauses cam guide 302 to move rearwardly toward motor 121' such that pins432 engage the rear stop surfaces of slots 428 for pivoting lift andtilt linkage 97' in the manner heretofore described. As is apparent,selective actuation of switch 275 for reversing the rotation of screwshaft 129 in the second opposite direction causes chair assembly 300 tobe lowered for returning to the normal seating position of FIG. 8A.However, in accordance with the teachings of the present invention,continued rotation of shaft 129 in the second direction causes continuedforward movement of cam guide 302 relative to screw 129. Pins 432 moveforwardly through slot 428 until the first cam surface 452 formed on theunderside of cam guide 302 engages first roller 450 supported on firstcam lever 442 of first follower assembly 304.

In comparing FIGS. 10 and 12, first roller 450 is shown in FIG. 10 in aneutral position of non-engagement with first cam surface 452 and, inFIG. 12 in a position of contact with respect to first cam surface 452that corresponds to full extension of leg rest assembly 13. As such, itwill be appreciated that forward movement of cam guide 302 pivotablydrives first follower assembly 304 about torque tube 430 such that firstcam link 446 drives toggle link 454 which, in turn, drives connectorlink 456 for rotating drive shaft 15. In this manner, pantograph legrest linkages 332 are protracted to their extended position of FIG. 12.Such rotation of drive shaft 15 extends pantograph linkages 332 in aknown manner.

Adjacent first cam surface 452 is a generally planar surface 453 which,upon full extension of leg rest assembly 13, first roller 450 continuesto ride against upon continued forward movement of cam guide 302. Thisplanar surface 453 permits continued forward movement of cam guide 302without generating any additional rotation of drive shaft 15. Leg restassembly 13 can be returned to its retracted position by simplyreversing the rotation of screw shaft 129 for moving cam guide 302rearwardly so as to permit springs 480 to rearwardly rotate first camfollower assembly 304. In this manner, the present invention includesspring-biased return means instead of power return typically associatedwith conventional power-assisted chair units. This is desirable in thatthis spring-biased return means generates a significantly reduced returnforce as compared to systems having a power return feature.

According to the present invention, upon full extension of leg restassembly 13 via first cam surface 452 drivingly moving first followerassembly 304, continued forward movement of cam guide 302 causesengagement between second roller 451 of second follower assembly 306 andsecond cam surface 470 (See FIG. 13) for forwardly driving second camlink 466 which, in turn, forwardly drives (i.e. pulls) tubular cross bar424 for reclining chair 300 in the manner described. Preferably, aslight amount of cam guide linear displacement along screw shaft 129 isprovided between the end of the point of contact of first follower 450and first cam surface 452 and the beginning of contact by secondfollower 451 and second cam surface 470 such that the seat occupant mayfully extend leg rest assembly 13 without initiating reclining movement.

As was previously described, switch means are preferably provided at theforward and rearward ends of screw shaft 129 for terminating rotationthereof. A shown in FIG. 10 a limit switch 440 is provided which isadapted to contact a portion of cam guide 302, such as pin 432, forterminating rotation of screw shaft 129 once cam guide 302 has movedforwardly to a position defining a fully reclined seating position withleg rest assembly 13 also fully extended (FIG. 13). A rear limit switch141 is provided on motor 121 to define a maximum forward tilted positionfor lift and tilt linkage 97'.

As will be appreciated, the present invention can be easily modified toinclude one or both of first and second follower assemblies 304 and 306,respectively. As shown, actuation is sequential when both followerassemblies are utilized. As such, it is possible to manufacture variouscombination recliner chairs 300 by simply eliminating one of therespective follower assemblies or rendering one of the followerassemblies inoperative. Furthermore, drive mechanism 301 is adapted forsimple installation into conventional manually actuated drive systemswithout a significant number of new parts or design changes beingrequired.

Chair 300 is especially useful for invalids since by pressing switch 275the occupant can change his position on the seat to provide greatercomfort when desired. If the disability of the occupant is such as torender the occupant unable to reach switches mounted on the side ofchair 300, it is within the purview of the invention to provide a switchbox which may rest on his lap and be operated by the simple movement ofa finger.

The foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. One skilled in the art willreadily recognize from such discussion, and from the accompanyingdrawings and claims, that various changes, modifications and variationscan be made therein without departing from the spirit and scope of theinvention as defined in the following claims.

What is claimed is:
 1. A power-assist chair comprising:a base assembly;a chair frame pivotally supported on said base assembly; a seat assemblyhaving a seat member, a seat back and swing link means for pivotallyinterconnecting said seat back and said seat member to said chair framefor reclining movement between an upright position and a reclinedposition; a rotatable drive shaft extending transversely betweenopposite side portions of said chair frame; a leg rest assemblysupported from said chair frame and operatively coupled to said driveshaft for movement between a retracted position upon rotation of saiddrive shaft in a first direction, and an extended position upon rotationof said drive shaft in a second direction; follower means supported forpivotal movement on said base assembly and operably interconnected tosaid drive shaft; linear actuation means for actuating said leg restassembly, said linear actuation means including a cam guide memberadapted for translational movement and having cam surface meansengageable with said follower means for causing corresponding rotationof said drive shaft in said second direction so as to extend said legrest assembly; and spring return means for biasing said follower meansin opposition to said cam surface means such that said leg rest assemblyis biased toward said retracted position.
 2. The power-assist chair ofclaim 1 wherein said linear actuation means comprises an electric motor,a screw shaft rotatably driven by said motor, and wherein said cam guidemember has internal threads received on said screw shaft such thatselective energization of said motor causes said screw shaft to rotatein a first direction for causing forward movement of said cam guidetoward said follower means, and wherein said motor may be energized forgenerating rotation of said screw shaft in an opposite second directionfor causing rearward movement of said cam guide away from said followermeans.
 3. The power-assist chair of claim 2 wherein said follower meansincludes a cam lever adapted to engage said cam surface means of saidcam guide member, and linkage means operatively coupling said cam leverto said drive shaft, whereby forward movement of said cam guide membercauses said cam surface means to engage said cam lever for pivoting saidcam lever such that said linkage means generates corresponding rotationof said drive shaft for moving said leg rest to said extended position.4. The power-assist chair of claim 1 wherein said leg rest assemblyincludes pantograph linkage means operatively connected to said driveshaft such that rotation of said drive shaft moves said leg restassembly and movement of said leg rest assembly moves said drive shaft,and wherein said spring return means includes a spring interconnectingsaid pantograph linkage means to said base assembly such that uponrearward movement of said cam guide member said spring urges saidpantograph linkage toward its retracted position.
 5. The power-assistchair of claim 1 further comprising lift means operativelyinterconnecting said chair frame to said base assembly for elevating andtilting said chair frame, said lift means operatively associated withsaid linear actuation means such that rearward movement of said camguide actuates said lift means to move said chair frame to anelevated-tilted position and forward movement of said cam guide lowerssaid chair frame from said elevated-tilted position to a normal seatingposition.
 6. A power-assist chair of claim 5 wherein said lift meanscomprises a stationary rectangular lower frame adapted to rest on afloor, a movable rectangular upper frame, said upper frame providingsupport means on which said chair frame is mounted, a lift bar memberpivoted at one end to a central portion of said lower frame andextending longitudinally forwardly from said pivot and being locatedsubstantially within the confines of said lower frame when said liftmeans is in a fully lowered position, the other and front end of saidlift bar member being pivoted to the front end of said upper frame, saidmotor being pivoted to a rear portion of said lower frame for arcuatemotion of said screw shaft in a vertical plane, bracket means supportedon said lift bar which extend upwardly within the confines of said upperframe when said lift means is in said lowered position and which defineelongated slots, said cam guide member having pins extending throughsaid elongated slots in said bracket means, whereby rearward movement ofsaid cam guide member along the length of said screw shaft until saidpins engage a rearward end of said slots causes said cam guide member toelevate said upper frame, and wherein forward longitudinal movement ofsaid cam guide lowers said upper frame, said lift means furtherincluding tilt linkage means connected to said upper frame for pivotingsaid upper frame about a pivot axis of said lift bar when said upperframe is elevated or lowered.
 7. The power-assist chair of claim 6wherein said lift means is adapted to move said chair frame to saidelevated-tilted position from said normal lowered position upon said camguide member being moved rearwardly from a neutral position ofnon-engagement with said follower means, wherein forward movement ofsaid cam guide member toward said neutral position causes said chairframe to move toward said normal lowered position from saidelevated-tilted position, and wherein said leg rest assembly is adaptedto be actuated from said normal lowered position upon said cam guidemember moving forwardly beyond said neutral position.
 8. A power-assistchair of claim 6 wherein said tilt linkage means comprises a tilt barmember pivoted at its rear end to said lower frame and extendinglongitudinally forwardly from said rear end pivot and being locatedsubstantially within the confines of said upper frame when said liftmeans is in said lowered position, the front end of said tilt bar memberbeing pivoted to the front end of said lower frame.
 9. A power-assistchair comprising:a base assembly; a chair frame pivotally supported onsaid base assembly; a seat assembly having a seat member, a seat backand swing link means for pivotally interconnecting said seat back andsaid seat member to said chair frame for reclining movement between anupright position and a reclined position; a rotatable drive shaftextending transversely between opposite side portions of said chairframe; a leg rest assembly supported from said chair frame andoperatively coupled to said drive shaft for movement between a retractedposition upon rotation of said drive shaft in a first direction, and anextended position upon rotation of said drive shaft in a seconddirection; follower means supported for pivotal movement on said baseassembly and operably interconnected to said swing link shaft; linearactuation means for actuating said swing link means, said linearactuation means including a cam guide member adapted for translationalmovement and having cam surface means engageable with said followermeans for causing corresponding rotation of said swing link means so asto move said seat assembly to said reclined position; and spring returnmeans for biasing said follower means in opposition to said cam surfacemeans such that said swing link means is biased toward said uprightposition.
 10. The power-assist chair of claim 9 wherein said followermeans include s cam lever adapted to engage said cam surface means, andlinkage means operatively coupling said cam lever to said swing linkagemeans, whereby continued forward movement of said cam guide membercauses said cam surface means to engage said cam lever for pivoting saidcam lever such that said linkage means generates corresponding movementof said swing link means for moving said seat assembly to said reclinedposition.
 11. The power-assist chair of claim 10 wherein said swing linkmeans includes a first pair of swing linkages supported on opposite rearside portions of said chair frame and interconnecting said seat assemblyto said chair frame, said first pair of swing linkages interconnected bya transverse cross member which is operatively coupled to said linkagemeans for moving said swing link means forwardly upon said cam guidemember pivotably moving said cam lever.
 12. The power-assist chair ofclaim 11 wherein said swing link means further includes a second pair ofswing linkages supported between and operatively interconnecting frontside portions of said chair frame and said seat member, said second pairof swing linkages being adapted to tilt said chair frame relative tosaid base assembly during extension of said leg rest assembly and topull said seat member forwardly upon forward movement of said crossmember.
 13. The power-assist chair of claim 9 wherein said spring returnmeans includes a spring member interconnecting said follower means tosaid base assembly such that upon rearward movement of said cam guidemember said spring member urges said swing link means rearwardly suchthat said chair frame is biased toward said upright position.
 14. Thepower-assist chair of claim 9 further comprising lift means operativelyinterconnecting said chair frame to said base assembly for elevating andtilting said chair frame, said lift means operatively associated withsaid linear actuation means such that rearward movement of said camguide actuates said lift means to move said chair frame to anelevated-tilted position and forward movement of said cam guide lowerssaid chair frame from said elevated-tilted position to a normal seatingposition.
 15. A drive mechanism for use in power-assisted chairs of thetype having a base, a chair frame supported on the base, an extensibleleg rest assembly and a reclinable seat assembly, said drive mechanismcomprising:shaft means for operatively connecting said leg rest assemblyto said chair frame, said shaft means operable for rotation in a firstdirection for moving said leg rest assembly to an extended position, andsaid shaft means rotatable in an opposite second direction for movingsaid leg rest assembly to a retracted position; a follower assemblysupported for pivotal movement on said base; linkage means operativelycoupling said follower assembly to said shaft means; linear actuationmeans for selectively actuating said leg rest assembly, said linearactuation means including a cam guide member adapted for translationalmovement and having cam surface means engageable with said followerassembly for causing said shaft means to rotate in said first directionfor extending said leg rest assembly; spring return means operativelyinterconnecting said follower assembly and said leg rest assembly tosaid base for biasing sad leg rest assembly toward a retracted position;and said linear actuation means including power operated means adaptedto selectively moving said cam guide member in a first direction towardsaid follower assembly and in a second direction away from said followerassembly.
 16. The drive mechanism of claim 15 wherein said followerassembly includes a cam lever adapted to engage said cam surface meansof said cam guide member, said linkage means operatively coupling saidcam lever to said shaft means, whereby forward movement of said camguide member causes said first cam surface means to engage said camlever for pivoting said cam lever such that said linkage means generatescorresponding rotation of said shaft means for moving said leg restassembly to said extended position.
 17. The drive mechanism of claim 15wherein said spring return means is a spring member interconnecting saidlinkage means to said base such that upon rearward movement of said camguide member said spring member biases said follower assembly for urgingsaid leg rest assembly toward its retracted position.
 18. The drivemechanism of claim 15 wherein said power operated means comprises anelectric motor, a screw shaft rotatably driven by said motor, andwherein said cam guide member has internal threads received on saidscrew shaft such that selective energization of said motor causes saidscrew shaft to rotate in a direction causing forward translationalmovement of said cam guide toward said follower assembly, and whereinsaid motor may be energized for generating rotation of said screw shaftin an opposite direction for causing rearward translational movement ofsaid cam guide away from said follower assembly.
 19. The drive mechanismof claim 18 further comprising lift means operatively interconnectingsaid chair frame to said base for elevating and tilting said chairframe, said lift means operatively associated with said power operatedmeans such that rearward movement of said cam guide actuates said liftmeans for moving said chair frame to an elevated-tilted position andforward movement of said cam guide lowers said chair frame from saidelevated-tilted position to a lowered seating position.
 20. A drivemechanism for use in power-assisted chairs of the type having a base, achair frame supported on the base, an extensible leg rest assembly and areclinable seat assembly having swing linkages pivotally interconnectinga seat back and a seat frame relative to the chair frame, said drivemechanism comprising:shaft means for operatively connecting said legrest assembly to said chair frame, said shaft means operable forrotation in a first direction for moving said leg rest assembly to anextended position, and said shaft means rotatable in an opposite seconddirection for moving said leg rest assembly to a retracted position; afollower assembly supported for pivotal movement on said base; linkagemeans interconnecting said follower assembly to said swing link means;linear actuation means for actuating said swing link means, said linearactuation means including a cam guide member adapted for translationalmovement and having cam surface means adapted to engage said followerassembly for causing said swing linkages to move said seat assembly froman upright position to a reclined position; spring return meansoperatively interconnecting said follower assembly to said base forbiasing said seat assembly to said upright position; and said linearactuation means including power operated means adapted for selectivelymoving said cam guide member in a first direction toward said followerassembly and in a second direction away from said follower assembly. 21.The drive mechanism of claim 20 wherein said follower assembly includesa cam lever adapted to engage said cam surface means, said linkage meansoperatively coupling said cam lever to said swing linkage, wherebycontinued forward movement of said cam guide member causes said camsurface means to engage said cam lever for pivoting said cam lever suchthat said second linkage means generates corresponding movement of saidswing linkage for moving said seat assembly to said reclined position.22. The drive mechanism of claim 20 wherein said spring return meansincludes a spring member interconnecting said follower assembly to saidbase such that upon rearward movement of said cam guide member saidspring member urged said swing linkage rearwardly such that said chairframe is biased toward said upright position.
 23. The drive mechanism ofclaim 20 wherein said power operated means comprises an electric motor,a screw shaft rotatably driven by said motor, and wherein said cam guidemember has internal threads received on said screw shaft such thatselective energization of said motor causes said screw shaft to rotatein a direction causing forward translational movement of said cam guidetoward said follower assembly, and wherein said motor may be energizedfor generating rotation of said screw shaft in an opposite direction forcausing rearward translational movement of said cam guide away from saidfollower assembly.
 24. The drive mechanism of claim 23 furthercomprising lift means operatively interconnecting said chair frame tosaid base for elevating and tilting said chair frame, said lift meansoperatively associated with said power operated means such that rearwardmovement of said cam guide actuates said lift means for moving saidchair frame to an elevated-tilted position and forward movement of saidcam guide lowers said chair frame from said elevated-tilted position toa lowered seating position.